Difference Between Soldering, Welding And Brazing

What Is Welding?

Welding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics by using high heat to melt the parts together and allowing them to cool causing fusion. As opposed to brazing and soldering, which do not melt the base metal, welding is a high heat process which melts the base material, typically with the addition of a filler material.

The high heat causes a weld pool of molten material which cools to form the joint, which can be stronger than the parent metal. Pressure can also be used to produce a weld, either alongside the heat or by itself. Welding can also use a shielding gas to protect the melted and filler metals from becoming contaminated or oxidized.

Types Of  Welding

• Electric resistance welding
• Gas metal arc welding
• Gas tungsten arc welding
• Glass welding
• Plastic welding
• Shielded metal arc welding

What You Need To Know About Welding

• Welding is a process that uses heat to melt down and fuse two metallic objects.
• Welding joints are strongest joints. The strength of the welded portion of joint is often more than the strength of base metal.
• The temperature needed to weld two metals together must be very high (above 1000^◦C) so that they melt and join.
• In welding, the work piece needs to be heated up to their melting point.
• Before the process of welding, there is no preheating of the work piece since welding itself is carried out at high temperatures.
• Due to heating and cooling, the mechanical properties of base metal may change at the joint.
• Heat cost is involved and high skill level is required.
• Welding is suitable with thicker as well as similar or dissimilar metal parts.
• In welding, combinations of carbonate and silicate materials are used as flux to shield the weld from atmospheric gases.
• A metal alloy is used as filler in welding. Some metals such as lead or Birmabright aluminum alloy use offcut strips of the same metal as filler.

What Is Soldering?

Soldering is a process in which two or more items are joined together by melting and putting a filler metal into the joint, the filler metal having a lower melting point than the adjoining metal. Unlike welding, soldering does not involve melting the work pieces.

In soldering, a soldering iron is used to heat the solder usually from an electrical supply at high temperatures above the melting point of the metal alloy. This allows for the solder to flow between the workpieces needing to be joined.  A soldering iron tool is made up of an insulted handle and a heated pointed metal iron tip.

Soldering is used in plumbing, electronics and metalwork from flashing to Jewellery and musical instruments. Soldering provides reasonably permanent but reversible connections between copper pipes in plumbing systems as well as joints in sheet metal objects such as food cans, roof flashing, rain gutters and automobile radiators.

Types of Soldering

There are two types of soldering which use increasingly higher temperatures, which in turn produce progressively stronger joints.

• Hard soldering – Brass or silver is the bonding metal used in this process and requires a blowtorch to achieve the temperatures at which the solder melts.
• Soft soldering– Soft soldering  has the lowest filler metal melting point at less than 400^◦C. Due to low temperatures, soft soldering thermally stresses components the least but does not make strong joints and is then therefore unsuitable for mechanical load-bearing applications.

What You Need To Know About Soldering

• Soldering is can be described as a metal joining process where the melting temperature of the filler metal is relatively low.
• Soldering joints are weakest joints out of the three. The joints are not meant to bear the load. They are generally used to make electrical contact.
• Soldering is usually done at temperature below 200 ^◦C.
• In soldering, heating of the work piece is not a requirement.
• Before the process of soldering, there is preheating of work piece so as to have good quality joints.
• After the process of soldering, mechanical properties of base metal does not change.
• The cost involved and skill requirements are very low.
• Soldering is possible only in case of thin as well as similar sheet metals.
• In soldering, zinc and rosin are generally used as flux.
• A Solder is used as a metal filler in soldering a. A solder is an alloy of lead and tin.

Also Read: Difference Between AC And DC Welding

What Is Brazing?

Brazing is a metal-joining process in which two or more metal items are joined together by melting and flowing a filler into the joint, the filler metal having a lower melting point than the adjoining metal. The filler metal is brought slightly above its fusion temperature; molten filler metal is then spread into the joint by capillary action. Molten filler metal subsequently solidifies as it cools and joins the workpieces together. The filler metals used for brazing are copper alloys.  

Brazing differs from welding in that it does not involve melting the work piece and from soldering in using higher temperatures for a similar process, while also requiring much more closely fitted parts than when soldering. Properly brazed joints can be stronger than the pieces joined by soldering, but are not as strong as welded joints.

Brazing can join dissimilar metals such as aluminum, silver, copper, gold and nickel. Flux is often used during brazing. It is a liquid that promotes wetting, which lets the filler flow over the metal parts to be joined. It also cleans the parts of oxides so that the filler bonds more tightly to the metal parts. In addition, fluxes are used in welding to clean the metal surface. 

Brazing is a widely used joining process because it can join almost all metal except aluminum and magnesium. It is used for electrical components, pipe fittings etc. Also, metals having uneven thickness can be joined by brazing.

Types of Brazing  

• Torch brazing
• Furnace brazing
• Braze welding
• Cast-iron welding
• Vacuum brazing

What You Need To Know About Brazing

• Brazing is a metal-joining process where the melting temperature of the filler metal is above 400 ͦC.
• Brazing joints are weaker than welding joint but stronger than soldering joints. The joints can bear the load up to some limits.
• Brazing is done at a temperature above 450^◦C but below the critical temperature of that metal.
• In Brazing, the work piece are heated but below their melting point.
• Given that brazing is carried out at relatively low temperatures, preheating is very much necessary so as to make the joints strong.
• After the process of brazing, there may be change in mechanical properties of the joint; however in most cases the change is negligible.
• Cost and skills are required.
• Brazing is suitable with thinner and thicker as well as similar or dissimilar metal parts.
• In brazing, ash and borax is used as flux.
• A Spelter is used in brazing as metal filler. A spelter is an alloy of copper and zinc.

Also Read: Difference Between TIG And MIG Welding

Difference Between Soldering, Welding And Brazing In Tabular Form